Kurzweil SP5-8 Service Manual

Printed Circuit Boards
Function Overview
2-7
DC power input jack and voltage regulators
(page 2, zones B4–B6)
J7 receives +15V 1.0A power from the external power adapter. L4 and L5 provide RFI ltering
and J6 connects to the power switch.
U11 is a switching regulator which provides +5V at high eciency for on-board circuits and
the Engine PCB. Note the minimum load spec of 0.25A. Typical load is about 1.0A. U10 is a
low current linear regulator which supplies +10V to the audio circuits.
-10V for the audio circuits is created by a charge pump (D36, D37, C13, C14) from the high-
power 15V rectangular wave produced by the switching regulator. R27 limits surge currents
at startup and ripple currents in the charge pump lter. Even though -10V is not strictly
regulated, it is very quiet in the audio range and suitable for analog use. Typical voltage
range is -8V to -12V.
USB connector interface
(page 2, zone A5)
The USB jack connects directly to the USB Control and Data cables that go to the Engine
PCB. Note that the Data cable must be constructed from special USB rated shielded cable for
reliable operation in high speed mode.
LCD contrast voltage adjuster
(page 2, zone C5)
VR1 is the front panel contrast control for the LCD. Resistors R25 and R119 set the voltage
range and center value so that optimum contrast is achieved near the center of the control’s
range. Since LCD operating voltages vary by vendor, the values in a particular unit may
be dierent from those in the schematic. Conversely, using a dierent vendor’s LCD may
require a change in one or more of these resistors.
Left Front Panel PCB
Switch Pedals and CC Pedal connectors and interface
(page 2, zone C6–D6)
J13 (Sustain) and J18 (Sustentuto) are the switch pedal inputs. The switch pedals close when
pressed. Their signals enter the Analog Multiplexor described below.
J12 is the Expression Pedal jack and expects a 3-terminal potentiometer with the wiper on
the tip (pin 2). The 5.1V reference voltage is supplied through a current limiter (Q6 and R37)
to the ring (pin 3). R45 pulls the wiper up to 5V when no pedal is plugged in thus ensuring
stable full volume. The wiper voltage is ltered and overvoltage protected by R44, C31, D39,
and D40.

Kurzweil SP5-8 Specifications

General

Keyboard number of keys	88
MIDI-keyboard number of keys	- keys
Product color	Black
Pitch bend wheel	Yes
Interface	USB
Headphone outputs	1
Input voltage	15 V
Power source type	DC
Power consumption (typical)	15 W

Weight and Dimensions

Depth	350 mm
Width	1392 mm
Height	120 mm
Weight	21000 g